Mobile cellular communication is evolving beyond traditional voice telephony towards more sophisticated services, such as Push-To-Talk (PTT). Similar to conventional walkie-talkie communication, PTT is a type of Voice Over IP (VOIP) communication that enables mobile communication users to send a voice message to one or more recipients over a mobile phone by simply pushing a key (i.e., PTT button, etc.).
One particular version of PTT, called PoC (PTT-over-Cellular), has started to be implemented in wireless data networks such as GSM/GPRS and CDMA cellular networks. By using internet protocols (i.e., an internet protocol network), these networks can provide a packet-based data service that enables information to be sent and received across a mobile telephone network. In addition, the use of internet protocols also facilitates PoC through the use of instant connections. That is, information can be sent or received immediately as the need arises, subject to available time slots at the air interface.
It is desirable to be able to provide users a log of received VOIP calls so that they may, for example, take note of missed calls. The desired call log functionality is similar to that which is common to most cell phones, in which a log of received calls and missed calls are stored in the cell phone. However, integration of call logs within phones with the VOIP client in such a way as to provide dual purpose logs (VOIP and circuit switched) is problematic for two primary reasons:
First, the integrated log API changes from device to device, thus adding complexity to a porting effort. Porting would require VOIP client customization to support a particular logging API.
Second, the integrated log APIs may only support a string as an entry without providing for multiple fields. PTT logs require a SIP URI and other PTT-specific information. Thus, the integrated log may not be fully functional as a PTT log.
PoC is discussed in greater detail in the following technical specifications which are incorporated by reference: Push-to-talk over Cellular (PoC), Architecture, PoC Release 2.0, V2.0.8 (2004-06); Push-to-talk over Cellular (PoC), Signaling Flows—UE to Network Interface (UNI), PoC Release 2.0, V2.0.6 (2004-06); and Push-to-talk over Cellular (PoC) User Plane, Transport Protocols, PoC Release 2.0, V2.0.8 (2004-06); PoC XDM Specification, OMA-PoC_XDM_Specification-V1—0-20041118-D; Shared XDM Specification, OMA-Shared_XDM_Specification-V1—0-20041118-D; OMA PoC Control Plane, OMA-POC-Control-Plane-V1—0-20041118-D; XML Document Management (XDM) Specification, OMA-XDM_Specification-V1—0-20041118-D; Authorizing who can subscribe to XCAP change event package, OMA-XDM_Specification-V1—0-20041118-D; Sample XCAP Call Flows, OMA-XDM_Specification-V1—0-20041118-D.
Of note, Release 1.0 is also available from the PoC Consortium as well as an upcoming PoC standard from Open Mobile Alliance (OMA). All of these are generally considered native PoC standards. Subsequently, a UE (user equipment), such as a PoC enabled cellular phone, supporting either of these standards is called a native PoC client. Additional information is found in IETF RFC 3261, which is incorporated herein by reference. This document describes Session Initiation Protocol (SIP), which is an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants. These sessions include Internet telephone calls, multimedia distribution, and multimedia conferences.